Ruby & Machine Vision - Talk at Sheffield Hallam University Feb 2009

Ruby & Machine Vision

Ruby & Machine Vision

Jan Wedekind

Wednesday, February 4th 2009

Wednesday, February 4th 2009 http://vision.eng.shu.ac.uk/jan/demfeb09.pdf 1/38

UK EPSRC Nanorobotics Project

Microscopy Software
• telemanipulation
• drift
compensation
• closed-loop
control
Machine Vision
• real-time software
• system integration
• theoretical
insights


Ruby Programming Language

Ruby
• created by Yukihiro Matsumoto
• released 1995 (free software(*) , Ruby license)
• inspired by Perl, Python, Smalltalk, Eiﬀel, Ada, Lisp
• “pseudo simplicity”: simple syntax ⇔ multi-paradigm
language
• highly portable
• Tiobe Programming Community Index #11
• 1.8.6 being superseded by 1.9.1

page url

Ruby Homepage http://www.ruby-lang.org/
Ruby Core-API http://www.ruby-doc.org/
RubyForge http://rubyforge.org/
Ruby Application Archive http://raa.ruby-lang.org/

(*) http://www.gnu.org/philosophy/free-sw.html


Dynamic Typing

#!/usr/bin/env ruby
def test( a, b )
a + b
end
x = test( 3, 5 ) # x -> 8
x = test( 'a', 'b' ) # x -> 'ab'


Garbage Collector

Mark and Sweep Garbage Collector
root

marked=true marked=true marked=true

marked=false marked=false marked=true

http://www.brpreiss.com/books/opus5/html/page424.html


(Pure) Object-Oriented, Single-Dispatch

#!/usr/bin/env ruby
class Numeric
def plus(x)
self.+(x)
end
end
y = 5.plus 6
# y is now equal to 11

http://www.ruby-lang.org/en/about/


Mixins

#!/usr/bin/env ruby
module TimesThree
def three_times
self + self + self
end
end
class String
include TimesThree
end
'abc'.three_times # -> 'abcabcabc'


Exception Handling

#!/usr/bin/env ruby
begin
print "Enter filename: "
STDOUT.flush
file_name = STDIN.readline.delete( "nr" )
file = File.new file_name, 'r'
# ...
rescue Exception => e
puts "Error opening file '#{file_name}': #{e.message}"
end


Closures

Unifying Concept for Iterators, Function Objects, and Loops
#!/usr/bin/env ruby
def inc( i )
lambda do |v|
v + i
end
end
t = inc( 5 )
t.call( 3 ) # -> 8
[ 1, 2, 3 ].each do |x|
puts x
end
[ 1, 2, 3 ].collect do |x|
x ** 2
end # -> [1, 4, 9]
[ 1, 2, 3 ].inject do |v,x|
v + x
end # -> 6


Continuations

#!/usr/bin/env ruby
def test( c2 )
callcc do |c1|
return c1
end
c2.call
end
callcc do |c2|
c1 = test( c2 )
c1.call
end


Introspection

Program can “see” itself
#!/usr/bin/env ruby
x = 5 # -> 5
x.class # -> Fixnum
x.class.class # -> Class
x.class.superclass # -> Integer
x.is_a?( Fixnum ) # -> true
Fixnum < Integer # -> true
5.respond_to?( '+' ) # -> true
5.methods.grep( /^f/ ).sort # -> ["floor", "freeze", "frozen?"]


Metaprogramming

Interpreter modiﬁes Program
#!/usr/bin/env ruby
eval 'x=5' # x -> 5
a = [ 1 ]
a.instance_eval do
push 2
end # a -> [ 1, 2 ]
a.send( 'push', 3 ) # a -> [ 1, 2, 3 ]
Object.const_get( 'String' ).class_eval do
define_method 'test' do
reverse
end
end
'abc'.reverse # -> 'cba'


Reiﬁcation

Program modiﬁes Interpreter
#!/usr/bin/env ruby
class Numeric
def method_missing( name, *args )
prefix = Regexp.new( "^#{name}" )
full_name = methods.find { |id| id =~ prefix }
if full_name
send( full_name, *args )
else
super
end
end
end
5.mod 2 # calls 5.modulo 2


Ruby Extensions
C Library
// gcc -shared -fPIC -I/usr/lib/ruby/1.8/x86_64-linux
// -o myextension.so myextension.c
#include <ruby.h>
#include <math.h>

VALUE wrap_logx( VALUE self, VALUE x )
{
return rb_float_new( log( NUM2DBL( self ) ) / log( NUM2DBL( x ) ) );
}

void Init_myextension(void) {
VALUE numeric = rb_const_get( rb_cObject, rb_intern( "Numeric" ) );
rb_define_method( numeric, "logx", RUBY_METHOD_FUNC( wrap_logx ), 1 );
}

Invoking Ruby Program
#!/usr/bin/env ruby
require 'myextension'
e = 1024.logx( 2 )
puts "2 ** #{e} = 1024"

http://www.rubyist.net/~nobu/ruby/Ruby_Extension_Manual.html

HornetsEye - Ruby Extension for Machine Vision

Free Software Project
• Real-Time Machine Vision
• Ruby Extension
• released under GNU General Public License
• 2 years development
• 22000 lines of code

http://www.wedesoft.demon.co.uk/hornetseye-api/
http://rubyforge.org/projects/hornetseye/
http://sourceforge.net/projects/hornetseye/
https://launchpad.net/hornetseye/
http://raa.ruby-lang.org/project/hornetseye/


Using existing Free Software

Libraries Integrated
C++ Boost

libdc1394
Tools in Use
DotGNU
Bazaar
FFTW

MPlayer GCC

OpenEXR make, automake, autoconf
NaturalDocs
Qt4-QtRuby
RMagick NSIS

NArray Ruby

libxine

Xorg, Mesa3D


Inpput/Output Classes

Input/Output Classes

/
V4LInput VFWInput
V4L2Input DShowInput
DC1394Input —
XineInput —
MPlayerInput MPlayerInput
MEncoderOutput MEncoderOutput
X11Display W32Display
X11Window W32Window
XImageOutput GDIOutput
OpenGLOutput —
XVideoOutput —


Colourspace Conversions

      
Y 0.299 0.587 0.114 R 0
      
Cb  = −0.168736 −0.331264  G + 128
0.500    
   
Cr 0.500 −0.418688 −0.081312 B 128
also see: http://fourcc.org/


GUI Integration I/II


GUI Integration II/II


Just-In-Time Compiler

#!/usr/bin/env
require 'hornetseye'
include Hornetseye
fun = JITFunction.compile( JITType::DFLOAT,
JITType::DFLOAT,
JITType::DFLOAT ) do |f,a,b|
Math.log( a ) / Math.log( b )
end
fun.call( 1024, 2 ) # -> 10.0


Some other Vision Libraries I/II

Framewave
EasyVision
CMVision
Camellia

Gamera

Gandalf
libCVD

Filters
Blepo
feature

Camera Input
Image Files
Video Files
Display
Scripting
Warps
Histograms
Custom Filters
Fourier Transforms
Feature Extraction
Feature Matching
GPL compatible ?
Also see http://www.wedesoft.demon.co.uk/hornetseye-api/files/Links-txt.html


Some other Vision Libraries II/II

NASA V. W.
HornetsEye

ITK/VTK

SceneLib
OpenCV

VIGRA
Mimas
LTIlib

Lush
IVT
feature

Camera Input
Image Files
Video Files
Display
Scripting
Warps
Histograms
Custom Filters
Fourier Transforms
Feature Extraction
Feature Matching
GPL compatible
Also see http://www.wedesoft.demon.co.uk/hornetseye-api/files/Links-txt.html


Dense Scripts

OpenCV + Python

#! /usr/bin/env python
import sys
from opencv import cv
from opencv import highgui
highgui.cvNamedWindow( ’Camera’ )
capture = highgui.cvCreateCameraCapture( -1 )
while 1:
frame = highgui.cvQueryFrame( capture )
gray = cv.cvCreateImage( cv.cvSize( frame.width, frame.height), 8, 1 )
cv.cvCvtColor( frame, gray, cv.CV_BGR2GRAY )
highgui.cvShowImage( ’Camera’, gray )
if highgui.cvWaitKey( 5 ) 0:
break

HornetsEye + Ruby

#!/usr/bin/env ruby
require ’hornetseye’
include Hornetseye
capture = V4L2Input.new
X11Display.show { capture.read.to_grey8 }


Interactive Ruby (IRB)

include Hornetseye
img = MultiArray.load_rgb24 '/home/engjw/test/hornetseye/data/images/world.jpg'
# MultiArrayubytergb(640,320):
# [ [ RGB( 0, 20, 55 ), RGB( 0, 20, 55 ), RGB( 0, 20, 55 ), .... ],
# [ RGB( 17, 36, 69 ), RGB( 17, 36, 69 ), RGB( 18, 37, 70 ), .... ],
# [ RGB( 9, 24, 55 ), RGB( 9, 24, 55 ), RGB( 8, 23, 54 ), .... ],
# [ RGB( 8, 22, 51 ), RGB( 8, 22, 51 ), RGB( 7, 21, 50 ), .... ],
# [ RGB( 8, 19, 49 ), RGB( 8, 19, 49 ), RGB( 8, 19, 49 ), .... ],
# ....
filter = MultiArray.to_multiarray( [ [ 1, 1, 1 ], [ 1, 1, 1 ], [ 1, 1, 1 ] ] ).to_usint
# MultiArrayusint(3,3):
# [ [ 1, 1, 1 ],
# [ 1, 1, 1 ],
# [ 1, 1, 1 ] ]
img.correlate( filter )
# MultiArrayusintrgb(640,320):
# [ [ RGB( 34, 112, 248 ), RGB( 52, 169, 373 ), RGB( 54, 171, 375 ), .... ],
# [ RGB( 52, 160, 358 ), RGB( 78, 240, 537 ), RGB( 79, 241, 538 ), .... ],
# [ RGB( 68, 164, 350 ), RGB( 101, 245, 524 ), .... ],
# [ RGB( 50, 130, 310 ), RGB( 73, 193, 463 ), RGB( 72, 192, 462 ), .... ],
# [ RGB( 45, 123, 306 ), RGB( 66, 182, 458 ), RGB( 64, 182, 457 ), .... ],
# ....


Opening Webcam/Framegrabber

#!/usr/bin/env ruby
include Hornetseye
input = V4L2Input.new
img = input.read
img.show


Capture Image

#!/usr/bin/env ruby
include Hornetseye
input = V4L2Input.new
img = nil
X11Display.show { img = input.read_rgb24 }
img.save_rgb24 'test.jpg'


Capture Video

#!/usr/bin/env ruby
include Hornetseye
input = V4L2Input.new( '/dev/video0', 640, 480 )
output = MEncoderOutput.new( 'test.avi', 10,
'-ovc lavc -lavcopts vcodec=msmpeg4:vhq:vbitrate=4000' )
X11Display.show do
img = input.read
output.write( img )
img
end
output.close


Center of Gravity

#!/usr/bin/env ruby
include Hornetseye
input = V4L2Input.new '/dev/video0', 640, 480
idx = MultiArray.lint( input.width, input.height ).indgen!
x = idx % idx.shape[0]
y = idx / idx.shape[0]
img = nil
X11Display.show { img = input.read_rgb24 }
ref = img[ 0, 0 ]
X11Display.show do
img = input.read_rgb24.to_sintrgb
cdiff = img - ref
diff = cdiff.r.abs + cdiff.g.abs + cdiff.b.abs
mask = ( diff 40 ).to_ubyte
n = mask.sum
puts x = #{( mask * x ).sum / n}, y = #{(mask * y ).sum / n} if n 0
( img / 2 ) * ( mask + 1 )
end


David A. Forsyth, Jean Ponce - Computer Vision: A modern
Approach

Location: Adsetts Centre, Shelfmark: 006.37 FO (LEVEL 2)
http://catalogue.shu.ac.uk/search~S1/t?Computer%20vision:%20a%20modern%20approach


Hal Fulton - The Ruby Way

Location: Adsetts Centre, Shelfmark: 005.133 RUB FU (LEVEL 2)
http://catalogue.shu.ac.uk/search~S1/t?The%20Ruby%20way

Mark Pollefeys - Visual 3D modeling of real-world objects
and scenes from images

http://video.google.com/videoplay?docid=-1315387152400313941

Mark Pupilli - Particle Filtering for Real-time Camera
Localisation

http://www.cs.bris.ac.uk/home/pupilli/publications/thesis.pdf


Ben Bleything - Controlling Electronics with Ruby

http://rubyconf2007.confreaks.com/d1t2p1_ruby_and_electronics.html


Patrick Farley - Ruby Internals

http://mtnwestrubyconf2008.confreaks.com/11farley.html


Yukihiro Matsumoto - Does Language Matter?

http://rubyconf2007.confreaks.com/d2t1p8_keynote.html


Willow Garage, Inc.

http://www.willowgarage.com/


Thank You

This presentation was made with LT X,
A
E
TeXPower, InkScape, Ruby, and other
free software.

http://vision.eng.shu.ac.uk/jan/demfeb09.pdf

Ruby & Machine Vision - Talk at Sheffield Hallam University Feb 2009

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